AUTHOR=Milne Ricky J., Byrt Caitlin S., Patrick John W., Grof Christopher P.

TITLE=Are sucrose transporter expression profiles linked with patterns of biomass partitioning in Sorghum phenotypes?

JOURNAL=Frontiers in Plant Science

VOLUME=4

YEAR=2013

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2013.00223

DOI=10.3389/fpls.2013.00223

ISSN=1664-462X

ABSTRACT=<p><italic>Sorghum bicolor</italic> is a genetically diverse C<sub>4</sub> monocotyledonous species, encompassing varieties capable of producing high grain yields as well as sweet types which accumulate soluble sugars (predominantly sucrose) within their stems to high concentrations. Sucrose produced in leaves (sources) enters the phloem and is transported to regions of growth and storage (sinks). It is likely that sucrose transporter (SUT) proteins play pivotal roles in phloem loading and the delivery of sucrose to growth and storage sinks in all <italic>Sorghum</italic> ecotypes. Six <italic>SUTs </italic>are present in the published <italic>Sorghum</italic> genome, based on the BTx623 grain cultivar. Homologues of these <italic>SUTs</italic> were cloned and sequenced from the sweet cultivar Rio, and compared with the publically available genome information. SbSUT5 possessed nine amino acid sequence differences between the two varieties. Two of the remaining five SUTs exhibited single variations in their amino acid sequences (SbSUT1 and SbSUT2) whilst the rest shared identical sequences. Complementation of a mutant <italic>Saccharomyces</italic> yeast strain (SEY6210), unable to grow upon sucrose as the sole carbon source, demonstrated that the <italic>Sorghum</italic> SUTs were capable of transporting sucrose. <italic>SbSUT1</italic>, <italic>SbSUT4</italic>, and <italic>SbSUT6</italic> were highly expressed in mature leaf tissues and hence may contribute to phloem loading. In contrast, <italic>SbSUT2</italic> and <italic>SbSUT5</italic> were expressed most strongly in sinks consistent with a possible role of facilitating sucrose import into stem storage pools and developing inflorescences.</p>